The Impact of Mouthwash on Human Health

In many parts of our body, friendly bacteria assist us in regulating important physiological functions. The balance of our microbiome can help ward off disease and inversely, the imbalance can lead to many complications. Our oral microbiome is no different. Mouthwash is routinely recommended by oral health experts to control plaque and gingivitis. However, a recent study suggests that this common part of our morning routine could be causing more harm than good.

A healthy oral microbiome is linked to a healthy cardiovascular system. Bacteria in our mouths assist in converting dietary nitrate into nitric oxide, an essential cardiovascular signaling molecule. While the body converts arginine to nitric oxide through the process of endogenous nitric oxide synthase, oral microbes utilize bacterial nitrate reductases to reduce dietary nitrate to nitrite. Swallowing nitrite helps stimulate nitric oxide signaling.

Longitudinal studies and clinical trials have shown that chronic mouthwash use is associated with increased blood pressure and increased risk for prediabetes/diabetes and hypertension.(4)

Several commensal oral bacteria are able to reduce nitrate, primarily the genera Neisseria, Haemophilus, Granulicatella, Veillonella, Prevotella, Corynebacterium, Actinomyces, and Rothia. Nitrate reductase activity is highest in the posterior of the dorsum of the tongue, especially under anaerobic conditions, but is also present in dental plaque and in saliva and under aerobic conditions. There is significant inter- and intrapersonal variability in the abundance of nitrate-reducing species; the most variable nitrate-reducing species on the human tongue are Rothia dentocariosa and Haemophilus parainfluenzae, while Prevotella melaninogenica and Veillonella dispar are the most constant and most abundant nitrate-reducing species.(4)

Most available mouthwashes contain bactericidal ingredients such as chlorhexidine. Long-term use can disrupt the microflora of the mouth, driving out nitric oxide-producing bacteria. Without the supplementation provided by these beneficial microbes, cardiovascular health could decline and increase the risk of hypertension. A study found that one week of twice-daily use of chlorhexidine was accompanied by a significant rise in systolic blood pressure. Halting the use of chlorhexidine led to the recovery of nitric oxide-producing oral bacteria and blood pressure returning to pre-study levels.

While further studies are required to confirm causality, current data suggests that long-term use of mouthwash can lead to an increased risk of hypertension.

In 2017, it was found that 62% of Americans used a mouthwash or dental rinse. Some common mouthwashes have evidence-based benefits and a seal of acceptance from the American Dental Association. Prescribed mouthwashes can be useful for conditions such as halitosis and dental caries. Studies evaluating these products for safety criteria though are mostly short-term. Long-term prospective clinical trials should be considered to measure the systemic impact of mouthwashes in different populations. In the meantime, preserving the delicate balance of a healthy microbiome should be our top priority.

By Alexandra Lopez
Business Intelligence Associate


References: 1, 2, 3, 4